1. The Field of the Invention
The present invention relates generally to the manufacture of carbon nanomaterials. More particularly, the present invention relates to methods for manufacturing carbon nanostructures that have a high content of surface functional groups.
2. The Related Technology
Carbon materials have been used in a variety of fields as high-performance and functional materials. Pyrolysis of organic compounds is known to be a useful method for preparing carbon materials. For example, carbon materials can be produced by pyrolyzing resorcinol-formaldehyde gel at temperatures above 600° C.
Most carbon materials obtained by pyrolysis of organic compounds at temperatures between 600-1400° C. tend to be amorphous or have a disordered structure. Obtaining highly crystalline or graphitic carbon materials can be very advantageous because of the unique properties exhibited by graphite. For example, graphitic materials can be conductive and form unique nanomaterials such as carbon nanotubes. However, using existing methods it is difficult to make these well-crystallized graphite structures using pyrolysis, especially at temperatures less than 2000° C.
To acquire the graphitic structure at lower temperature many studies have been carried out on carbonization in the presence of a metal catalyst. The catalyst is typically a salt of iron, nickel, or cobalt that is mixed with carbon precursor. Using catalytic graphitization, graphitic materials can be manufactured at temperatures between 600° C. and 1400° C.
Recently, this method has been used to manufacture carbon nanotubes and other carbon nanostructures. The carbon nanostructures are manufactured by mixing a carbon precursor with iron nanoparticles and carbonizing the precursor to cause the carbon nanostructure to grow from or around the iron nanoparticles. The iron nanoparticles are removed from the material by treating with strong acids. The amorphous carbon is typically removed using an oxidizing agent such as potassium permanganate.